Quick Tip: Why the Mag Won't Lock in Your AR-15

Brownells Gun Techs Steve Ostrem and Caleb Savant talk about what to do when that magazine won't seat into your AR-15. If it's a brand-new rifle, the magazine catch MIGHT be installed a little too high in the receiver, which can prevent it from retaining the mag. But that's not a common problem. Caleb recommends this test: Insert an unloaded magazine in the rifle with the bolt closed, then slowly pull the bolt back. If you can feel it dragging on the magazine lips, you know you have an out-of-spec mag. More likely, you have a new magazine with a stiff spring and a full 30 rounds of ammo in it. You'll need to give it a really firm push to get it to seat. Steve suggests locking the bolt back, then pushing the magazine home. If it locks in place, you know the mag is just a little on the stiff side, and it's just going to need an extra-hard push to seat on a closed bolt. Until the magazine gets broken in, you can just seat it with the bolt open, or load only 28 or 29 rounds in it until the spring takes a set. If your rifle has worked fine in the past with the same magazine, check the magazine catch for debris or damage that prevents it from grabbing the mag securely.

[Eric_Allen]

"if you've ever had a magazine fall out because it wasn't seated go ahead and hit that subscribe button" - Garand Thumb

[dl]

"Shove it!" is an instruction, not an insult, when speaking of magazines.

[siestatime]

Synchronized Sipping - the newest Olympic sport.

[Wwehrwolfoz]

Yep took 5 rounds out let some pressure off the new magazine spring and it functions like a champ, thanks for the simple fix

[shawnr]

Excellent advice.

A way to check where the magazine catch is hitting the magazine. Use a crayon and coat the top edge of the magazine catch.
With bolt closed, push the magazine catch in, insert a magazine and hold it up. Then release the magazine catch a couple of times.
Then push the magazine catch in and remove the magazine. The crayon will mark on the magazine. You will know if the notch was miss cut.

As another person in the comments stated you can also try adjusting the magazine catch tension by pushing in on the magazine catch button and rotating the other side 360 degrees.
One direction tightens the other loosens.
This might be an issue for some weapons.

[starwarscrazy]

I used a magpul mag and realized that you can load 31 rounds in it when it is designed for 30 rounds. I was wondering why mag would not seat when bolt closed it was human error not counting rounds. Never in my life have i came across this with magazines usually when mags reaches its capacity you cant fit anymore in it no matter what . Learning curve for me hope this helps someone out this had me baffled for sure.

[thomasgoller]

I run mostly 30 rounders, a mixture of aluminum and magpul pmags but I recently got a couple 40 rd pmags. Had one that wouldn't seat even when hitting it with my palm. This was on my 16" carbine that I've never had this problem with before. Turns out I was loading the mag from an ammo can with loose ammo and I managed to put 41 rounds in the mag. Took it out and it seated perfectly

[ImaYam]

Of all the gun channels, this is always short original content....also 8.5/10 for today’s synchronized cup raise lol

[yukon]

On a self built lower, I had to screw in the mag release 1 turn. No problem with a half dozen different magazine manufacturers.

[cameronnightman]

You guys have been releasing some great content! Thanks for giving us tips, tricks, and treats!

[JerrBearTactical]

Thanks and you guys Have Yourself A Merry Christmas😉👍🇺🇸

[robertmoore]

I just purchased my first AR. it is a used but pristine Bushmaster XM15 E2S M4 Carbine. It came with a new 30 rd PMag. I purchased a new 30 rd Bushmaster mag as well. I couldn't get either mag to lock in when loaded, no matter how hard I slammed it in. I saw this video last night at work and as soon as I got home this morning, I locked the bolt back and both mags locked in without any issue. I'm going to pick up some used, broken in mags and see how they work while leaving my new mags loaded and in my carry bag.

[zh]

Simple solution, always buy from Brownells! I have only Brownells AR magazines and have worked perfectly for years in my Colt, FN and Aero. Lifetime guaranteed!!

[HB-kprl]

Nice to see my very polite and respectful homies again. Always doing the good work. I appreciate it. I load 28 rounds for easier reload with a closed bolt.

[terrypen]

0:05 As we learned in the ARMY, apply SPORTS (Slap, Pull, Observe, Release, Tap, Squeeze).

[onionhead]

Sometimes it’s as simple as the magazine catch not being screwed in far enough to the magazine release button. Seen that issue come into my shop a few times. Just screw it in one or two more turns and you’re good to go. 👍

[SmokinLoon]

One of the things that may help in explaining an issue with function concerning the M16/AR15 platform is going back to the roots of the design, or "why" it was designed this way. For instance, when the M16 was first being designed it was first and foremost a rifle for a infantryman. Typically, infantrymen run their magazines dry and are not performing "administrative/tactical" reloads, or replacing a partially full magazine. The magazine, first the 20rd and then the 30rd, was designed to be inserted with the bolt locked to the rear therefore there was no force to overcome to get the magazine fully inserted. If the magazine would have been designed with another 1/4in of length I believe this issue of being overly forceful to get a full magazine inserted on a closed bolt would have been resolved. Even today with the new magazines it is easier with the Lancer, Troy, PMags, etc, to get them seated vs the USGI/STANAG mags.

[ChuckBerrington]

One of the greatest channels on YouTube, your hard work is always appreciated.

[Mockturtlesoup]

I bought a proprietary ambi lower from a guy who runs his own machining shop, and I ended up having two things cause my pins to be super tight, which in turn caused my magazine to not lock in properly(well, not by just shoving it in at least, no matter how hard I tried, even with only 28 rounds loaded. Smacking the bottom of the mag worked every time though. Also, I'm talking about loading the gun with the bolt forward, with a loaded mag. Loading the mag into the lower without the upper on, or with the bolt locked back of course worked just fine as well.)
First, I tightened that rubber/silicone covered screw in the pistol grip too tightly(the one that is used to tighten the upper to lower fit.)
Secondly, the guy I bought the lower from sent some proprietary parts. One of them was a little tiny set screw that covered the spring that goes into the back of the receiver, under the end plate, so that the spring(which admittedly, I have lost before on other rifles) won't go flying out when/if you take the endplate off(and possibly to make it easier to install(?), but if I remember correctly it made it harder.)
The problem with this(at least as far as I could tell) was that the spring was still the same length as you would use in a "normal" lower, meaning it was putting a lot more pressure on the takedown pin.
I ended up taking the set screw out, and loosening the rubberized screw(I can't recall what those are called) in the pistol grip, and that fixed both problems(the tight pins, and the difficulty inserting the mag.) Also, over time the pins got looser and looser from shooting, which actually allowed me to tighten the screw up again, taking any play out from between the upper and lower.
Hope this helps anyone with a similar issue(again, shooting the rifle helps significantly with tight pins. Like a couple hundred rounds or so.)

[PANDEMIC]

I had that same problem, bought 2 brand new 20 round pro mags and if they’re loaded to full capacity, it either won’t click in or it’ll pop out within a few seconds of putting one in. Or it’ll pop out every time you smack the mag in. My AR works great with other mags, but these ones just need breaking in and I mean a lot of breaking in. Only shot a few rounds on one, the other hasn’t been used yet. But I did notice that if you take off a few rounds, it fits better but still pops out on its own. Then finally loaded it to 10 rounds and it fits much better. Even when you pull on it numerous times, it’s now a tight fit and stays put. So that’s how it will be until those particular mags get broken in more.

So that’s my experience with brand new mags is some work straight out of the box, and others will need less rounds loaded in to start with and need more breaking in because it’s a tight fit since they’re still brand new. Once that mag spring gets more broken in, you can load more rounds in. I’ve never had a problem with the mag release button not being tight enough, it’s usually having a brand new mag loaded to full capacity and never used as well is what sometimes will give you a little trouble. But then loading less and it fits in there nice and tight. And giving the mag numerous pulls will tell you if it’s in there all the way.